backends/quartz/btree_util.h

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/* btree_util.h: common macros/functions in the Btree implementation.
 *
 * Copyright 1999,2000,2001 BrightStation PLC
 * Copyright 2002,2004,2007,2008 Olly Betts
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of the
 * License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301
 * USA
 */

#ifndef OM_HGUARD_BTREE_UTIL_H
#define OM_HGUARD_BTREE_UTIL_H

#include "quartz_types.h"
#include "omassert.h"

#include <string.h>  /* memset */
#include "safeunistd.h" /* for close() */

#include <string>

/* The unit of access into the DB files is an unsigned char, which is defined
   as 'byte' with a typedef.

   Other integer values are built up from these bytes, either in pairs or fours.
   'int2' and 'int4' are signed types which will comfortably accommodate
   all 2 byte and 4 byte ranges:
*/

/*
   If a signed int cannot hold the full range of two bytes replace 'int' by
   'long' throughout the code.

   FIXME: surely if a signed int cannot hold the full range of two bytes,
   then the compiler violates ANSI?  Or am I misunderstanding...
*/

// FIXME: 65536 in Asserts below should really be block_size
inline int
GETINT1(const byte *p, int c)
{
    Assert(c >= 0);
    Assert(c < 65536);
    return p[c];
}

inline void
SETINT1(byte *p, int c, int x)
{
    Assert(c >= 0);
    Assert(c < 65536);
    p[c] = x;
}

inline int
GETINT2(const byte *p, int c)
{
    Assert(c >= 0);
    Assert(c < 65536 - 1);
    return p[c] << 8 | p[c + 1];
}

inline void
SETINT2(byte *p, int c, int x)
{
    Assert(c >= 0);
    Assert(c < 65536 - 1);
    p[c] = x >> 8;
    p[c + 1] = x;
}

inline int
get_int4(const byte *p, int c)
{
    Assert(c >= 0);
    Assert(c < 65536 - 3);
    return p[c] << 24 | p[c + 1] << 16 | p[c + 2] << 8 | p[c + 3];
}

inline void
set_int4(byte *p, int c, int x)
{
    Assert(c >= 0);
    Assert(c < 65536 - 3);
    p[c] = x >> 24;
    p[c + 1] = x >> 16;
    p[c + 2] = x >> 8;
    p[c + 3] = x;
}

int sys_open_to_read(const std::string & name);
int sys_open_to_read_no_except(const std::string & name);
int sys_open_to_write(const std::string & name);
void sys_unlink_if_exists(const std::string &filename);
// Return true on success
inline bool sys_close(int h) {
    return close(h) == 0;
}

std::string sys_read_all_bytes(int h, size_t max);
void sys_write_string(int h, const std::string &s);
int sys_flush(int h);

inline byte *zeroed_new(size_t size)
{
    byte *temp = new byte[size];
    if (temp) memset(temp, 0, size);

    return temp;
}

class fdcloser {
    public:
        fdcloser(int fd_) : fd(fd_) {}
        ~fdcloser() {
            if (fd >= 0) {
                sys_close(fd);
            }
        }
    private:
        int fd;
};

#endif /* OM_HGUARD_BTREE_UTIL_H */

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